Summary of Significant Accounting Policies - Concentration Risk (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Concentration Risk [Line Items]
Short-term deposits	$ 0.8	$ 0.1
Net sales | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk	62.00%	45.00%
Distributor To The U.S. Navy | Net sales | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk	49.00%	23.00%
Distributor To The U.S. Navy | Accounts receivable
Concentration Risk [Line Items]
Concentration risk	28.00%
Distributor To The U.S. Navy | Accounts receivable | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk		10.00%
Regional Commercial Lighting Retrofit Company | Net sales | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk	12.00%
Regional Commercial Lighting Retrofit Company | Accounts receivable
Concentration Risk [Line Items]
Concentration risk		41.00%
Distributor To U.S. Navy Combined With Sales To Shipbuilders | Net sales | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk	53.00%
Shipbuilder For U.S. Navy | Accounts receivable
Concentration Risk [Line Items]
Concentration risk	21.00%
Offshore Supplier | Accounts receivable | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk	21.00%	21.00%
Offshore Supplier | Accounts Payable | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk	44.00%	54.00%
Domestic Supplier | Accounts receivable | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk	12.00%